Variable air volume (VAV) air supply systems typically include heat exchangers for providing a source of heating or cooling, as required, to the air circulated through the air supply system. The heat exchanger is preferable maintained at a relatively constant temperature, while the volume of air circulated through the building air supply system is varied within predetermined limits to ensure that the temperature within the building is kept relatively constant.
In order to vary the volume of air circulated within the VAV system, several means have been previously employed to vary the fan throughput volume. These means have included variable speed direct current or eddy current motors, frequency inverters, two-speed fan motors, moveable inlet guide vanes and variable sheave drive pulley and belt systems. However, these means of controlling the fan have typically included a relatively complex electronic controller or a relatively large number of mechanical components, or both, and therefore have been relatively expensive to install and also have had high maintenance requirements.
Therefore, it is an object of the invention to provide an improved controller for operating a two speed fan motor in conjunction with inlet guide vanes for controlling the air volume throughput in a fan unit.
It is another object of the invention to provide such a controller which is inexpensive and easy to implement.
It is yet another object of the invention to provide such a controller as will be simple and have a low maintenance requirement.
These and other objects of the present invention will be apparent from the attached drawings and the description of the preferred embodiment that follows hereinbelow.